Dynamically Stable Transporter Controlled by Lean

ABSTRACT

A transporter for transporting a subject over a surface that may be irregular. The transporter includes a support platform for supporting a load, the loaded support platform defining fore-aft and lateral planes and characterized by a load distribution. A plurality of ground contacting elements are coupled to the support platform such that the transporter is statically stable with respect to tipping in the fore-aft plane. At least one of the plurality of ground contacting elements is driven by a motorized drive arrangement. A sensor module generates a signal indicative of the load distribution. Based at least on the load distribution, a controller commands the motorized drive arrangement.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of co-pending U.S. application Ser. No.11/672,743 filed on Feb. 8, 2007, herein incorporated by reference,which is a continuation application of U.S. application Ser. No.11/144,309, filed Jun. 30, 2005, which is a divisional application ofU.S. patent application Ser. No. 10/618,082, filed Jul. 11, 2003,entitled “Motion Control for a Transporter,” which claimed priority fromU.S. Provisional Patent Application Ser. No. 60/395,299, filed Jul. 12,2002, entitled “Control of a Transporter Based on Disposition of theCenter of Gravity,” which are hereby incorporated by reference, in theirentireties.

TECHNICAL FIELD

The present invention pertains to transporters and methods fortransporting a load which may be an individual, and more particularly tocontrolling motion of a transporter.

BACKGROUND ART

A wide range of vehicles having a motorized drive arrangement are knownfor conveying various subjects, either for purposive locomotion or forrecreational purposes. The means used by an operator to control motionof the motorized drive arrangement of varies greatly. For example, anoperator may manipulate an accelerator pedal to control forward motionof an automobile, while steering is typically accomplished using asteering wheel. Or the motion of a sporting vehicle may be controlled byrocking a foot board upon which a user is standing towards the front orrear, so as to mechanically move a throttle cable, as described in U.S.Pat. No. 4,790,548 (Francken). Based on the operator's physicalattributes for example, or the transporter's intended functionality,alternative methods for controlling motion of a transporter may bedesirable.

SUMMARY OF THE INVENTION

In a first embodiment of the invention there is provided a transporterthat includes a support platform for supporting a load, the loadedsupport platform defining fore-aft and lateral planes and characterizedby a load distribution. A plurality of ground contacting elements arecoupled to the support platform such that the transporter is staticallystable with respect to tipping in the fore-aft plane. At least one ofthe plurality of ground contacting elements is driven by a motorizeddrive arrangement. A sensor module generates a signal indicative of aposition of the load distribution of the loaded support platform. Basedat least on the load distribution, a controller commands the motorizeddrive arrangement.

In accordance with related embodiments of the invention, the pluralityof ground contacting elements include at least two wheels. The at leasttwo wheels may include a first wheel rotatable about a first axis and asecond wheel rotatable about a second axis, the second axis disposed aftof the first axis. The controller may be configured so that fore and aftmotion of the transporter is controlled by shifting the loaddistribution and/or a position of the center of gravity of the loadedsupport platform fore and aft. The controller may also be configured sothat lateral motion of the transporter is controlled by laterallyshifting the load distribution and/or position of the center of gravityof the loaded support platform. The transporter may include a userinterface, such as a joystick or a dial, wherein the controller commandsthe motorized drive based at least on a signal provided by the userinterface. The sensor module may include a force sensor, a load sensor,and/or an angular rate sensor such as a tilt sensor that may be, forexample, a gyroscope or inclinometer. An offset may be used ingenerating the signal. The offset may be adjustable via a user interfaceon the transporter or a remote control device. The controller maycommand the motorized drive arrangement so as to cause an accelerationof the transporter. The transporter may further include an externallyapprehensible indicator for providing an indication based on motion,such as acceleration. The indicator, which may be a light, may beviewable from behind the transporter.

In accordance with another embodiment of the invention, a method forcontrolling a transporter having a support platform for supporting aload is presented. The loaded support platform defines fore-aft andlateral planes and is characterized by a load distribution. Thetransporter includes a plurality of ground-contacting elements such thatthe transporter is statically stable with respect to tipping in thefore-aft plane, with a motorized drive arrangement driving at least oneof the plurality of ground-contacting elements. The method includesdetermining the load distribution of the loaded support platform, andcommanding the motorized drive arrangement based at least on the loaddistribution.

In accordance with another embodiment of the invention, a transporterincludes a support platform for supporting a load, the support platformdefining a fore-aft plane and a lateral plane. A plurality of groundcontacting elements are coupled to the support platform such that thesupport platform is statically stable with respect to tipping in thefore-aft and the lateral plane. A pivot element is pivotally coupled toat least one of the ground contacting elements such that the pivotelement is capable of being tilted by a user interface. A sensor modulegenerates a signal indicative of the tilt of the pivot element. Acontroller commands a motorized drive arrangement based on the tilt ofthe pivot element. The motorized drive arrangement drives at least oneof the plurality of ground contacting elements.

In related embodiments of the invention, the pivot element may becapable of tilting in at least the fore-aft plane. The plurality ofground contacting elements may include two laterally disposed wheelsrotatable around an axis, the pivot element pivotally coupled to theaxis. The pivot element may be flexibly coupled to the support platform,via, for example, at least one spring. The user interface may be ahandlebar coupled to the pivot element.

In accordance with another embodiment of the invention, a method forcontrolling a transporter has a support platform for supporting a load,the support platform defining fore-aft and lateral planes. Thetransporter includes a plurality of ground-contacting elements such thatthe transporter is statically stable with respect to tipping. Thetransporter further includes a pivot element pivotally coupled to atleast one of the ground contacting elements such that the pivot elementis capable of tilting, and a motorized drive arrangement for driving atleast one of the plurality of ground-contacting elements. The methodincludes tilting the pivot element and commanding the motorized drivearrangement as a function of the tilt.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing features of the invention will be more readily understoodby reference to the following detailed description, taken with referenceto the accompanying drawings, in which:

FIG. 1 is an illustration of a side view of a transporter, in accordancewith one embodiment of the invention;

FIG. 2(a) is an illustration of a side view of a transporter, inaccordance with one embodiment of the invention;

FIG. 2(b) is an illustration of a side view of a transporter, inaccordance with one embodiment of the invention;

FIG. 3 is an illustration of a side view of a dynamically balancingvehicle;

FIG. 4 is a block diagram of a controller for controlling the motorizeddrive of a transporter, in accordance with one embodiment of theinvention; and

FIG. 5 is an illustration of a transporter, in accordance with oneembodiment of the invention.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

In accordance with one embodiment of the invention, FIG. 1 shows atransporter 10 for bearing a load, which may be a living subject, overthe ground or other surface, such as a floor, which may be referredherein as “ground.” Transporter 10 includes a support platform 11 forsupporting the load. A subject, for example, may stand or sit on supportplatform 11. Attached to support platform 11 may be a handlebar 12 thatcan be gripped while operating the transporter 10.

Coupled to the support platform 11 are a plurality of ground-contactingelements 13, 14, which provide contact between support platform 11 andthe ground. Ground-contacting elements may include, but are not limitedto, arcuate members, tracks, treads, and wheels (hereinafter the term“wheel” will be used in the specification to refer to any such groundcontacting element without limitation). Wheels 13, 14 help to define aseries of axes including the vertical axis, Z-Z, which is in thedirection of gravity through a point of contact of the wheel with theground; a lateral axis, Y-Y, which is parallel to the axis of thewheels, and a fore-aft axis, X-X, which is perpendicular to the wheelaxis. Directions parallel to the axes X-X and Y-Y are called thefore-aft and lateral directions respectively.

Transporter 10 is statically stable with respect to tipping in at leastthe fore-aft plane. To achieve static stability in the fore-aft plane,transporter 10 may include at least a first and second wheel 13, 14. Thefirst wheel 13 is rotatable about a first axis, and the second wheel 14is rotatable about a second axis that is aft of the first axis such thatthe center of gravity of the transporter 10 passes between the first andsecond wheel.

The motion of transporter 10 is controlled by shifting the loadedsupport platform's center of gravity. It is to be understood that “theposition of the center of gravity” as used herein is an example of amoment of a load distribution. Any mechanism for controlling the motionof the device based on the load distribution is within the scope of thepresent invention as described herein and as claimed in any of theappended claims. Shifting the position of the center of gravity may beaccomplished, for example, by a subject shifting his weight on supportplatform 11. To determine the shift in the center of gravity, thetransporter 10 includes a sensor module. The sensor module generates asignal indicative of a position of the center of gravity of the loadedsupport platform with respect to a fiducial point on the transporter 10.

Sensor module includes at least one sensor. The at least one sensor maybe, without limitation, a load sensor, a force sensor, and/or an angularrate sensor, such as a tilt sensor which may be, for example, agyroscope or an inclinometer.

Referring to FIG. 1 for example, transporter 10 includes two loadsensors 15, 16. Load sensor 15 is coupled between the support platform11 and the first wheel 13, while load sensor 16 is coupled between thesupport platform 11 and the second wheel 14. Using the sensed loadsabove each wheel 13 and 14, the position of the center of gravity alongthe fore-aft axis of the transporter 10 can be computed with respect toa fiducial point, such as, but not limited to, the front of the platform11. In various embodiments, a single load sensor may be used. Forexample, if the weight of the loaded support platform is known, thecenter of gravity can be determined using only the one load sensor.Changes in the output from the load sensor(s) that result from theshifting of the loaded support platform's center of gravity can also beused to control the motion of the transporter 10.

FIG. 2(a) shows another transporter 20, in accordance with oneembodiment of the invention. Transporter 20 includes a support platform21 that is allowed to tilt in the fore-aft plane, based for example, onthe platform's 21 center of gravity, while still being statically stablewith respect to tipping in at least the fore-aft plane. For example andwithout limitation, a pair of springs 26 and 25 may be coupled betweenwheels 23 and 24, respectively, and support platform 31. In otherembodiments, the ground contacting elements 23 and 24 may have somecompliance and serve the function of a spring. Based on the tilting ofthe support platform 21 in the fore-aft plane, at least one sensor 27generates a signal indicative, for example, of a position of the loadedsupport platform's center of gravity. Sensor 27 may be, withoutlimitation: a spring and associated sensor (such as a distance sensor);a load sensor; a tilt sensor such as an inclinometer or a gyroscopewhich provides an inclination of the support platform 21; whiskers; anangular rate sensor; and/or non-contact sensors, such as ultra-sonic oroptical. The tilt may be measured, without limitation, relative togravity, the ground, and/or a reference on the transporter, such as aposition proximate the axis of rotation. Attached to the supportplatform 21 may be a handlebar 22 that can be gripped while operatingthe transporter 20.

In another embodiment of the invention, FIG. 2(b) shows a transporter200 that includes a first support platform 290 and a second supportplatform 210. First support platform 290 is coupled to wheels 230 and240 so as to be statically stable with respect to tipping in thefore-aft plane. Second support platform 210 is coupled to the firstsupport platform 290 such that the second support platform 210 can tiltin the fore-aft plane based, for example, on the second platform's 210center of gravity. Second support platform 210 may be tiltably attachedto the first support platform using, without limitation, springs 250 and260 and/or a pivot mechanism 280. Similar to the above-describedembodiment, based on the tilting of the second support platform 210 inthe fore-aft plane, at least one sensor 270 generates a signalindicative of a position of the second support platform's 210 center ofgravity. Sensor 270 may be, without limitation: a spring and associatedsensor (such as a distance sensor); a load sensor; a tilt sensor such asan inclinometer or a gyroscope which provides an inclination of thesupport platform 507; whiskers; an angular rate sensor; and/ornon-contact sensors, such as ultra-sonic or optical. The tilt may bemeasured, without limitation, relative to gravity, the ground, the firstsupport platform 290 and/or another reference on the transporter.Attached to the first support platform 290 may be a handlebar 220 thatcan be gripped while operating the transporter 200.

In other embodiments of the invention, the transporter is staticallystable with respect to tipping in both the fore-aft and lateral planes.To provide such stability, the transporter may include three or morewheels. The center of gravity may then be determined in both thefore-aft axis and the lateral axis. For example, force or load sensorsmay be coupled between the support platform and each wheel, or a tiltsensor(s) may be utilized in combination with springs coupled betweeneach wheel.

In still other embodiments, transporter is statically stable withrespect to tilting in the lateral plane only, as in the case of thehuman transporter described in U.S. Pat. Nos. 5,701,965 and 5,971,091,which are herein incorporated by reference. For example, FIG. 3 shows apersonal transporter designated generally by numeral 38. The personaltransporter 38 includes a support platform 32. A handlebar 34 isattached to the support platform 32. A subject 30 stands on the supportplatform 32, so that the transporter 38 of this embodiment may beoperated in a manner analogous to a scooter. Leaning of the subject 30causes the support platform 32 to tilt, which is sensed by, withoutlimitation, a tilt sensor (not shown). A control loop is provided sothat lean of the subject 30 in a forward or backward direction resultsin the application of torque to wheel 33 about axle 35 thereby causingan acceleration of the vehicle. Vehicle 38, however, is staticallyunstable and requires operation of the control loop to maintain dynamicstability.

In the above-described embodiments, a controller receives the signalindicative of a position of the center gravity and/or tilt from thesensor module. Based at least on the position of the center of gravityand/or tilt, the controller commands a motorized drive arrangement fordriving one at least one of the plurality of wheels. The controller mayalso respond to commands from other operator interfaces, such as ajoystick or dial attached, for example, to a handlebar.

In accordance with one embodiment of the invention, the block diagram ofFIG. 4 shows a controller 40 for controlling the motorized drive of thetransporter. Controller 40 receives an input characteristic of aposition of the center of gravity and/or tilt of the loaded supportplatform from sensor module 44. Based at least on the input from thesensor module 44, controller 40 commands at least one motorized drive45, 46. Controller 40 also interfaces with a user interface 41 and awheel rotation sensor 43. User interface 41 may, for example, includecontrols for turning the controller 40 on or off. When the controller 40is turned off, the transporter's wheels may be free to move, such thattransporter acts as a typical push scooter. User interface 41 may alsocontrol a locking mechanism 42 for locking one or more wheels of thetransporter.

The controller 40 includes a control algorithm to determine the amountof torque to be applied to one or both wheels based on the position ofthe center of gravity and/or tilt of the loaded support platform. Thecontrol algorithm may be configured either in design of the system or inreal time, on the basis of current operating mode and operatingconditions as well as preferences of the user. Controller 40 mayimplement the control algorithm by using a control loop. The operationof control loops is well known in the art of electromechanicalengineering and is outlined, for example, in Fraser & Milne,Electro-Mechanical Engineering, IEEE Press (1994), particularly inChapter 11, “Principles of Continuous Control” which is incorporatedherein by reference.

As an example, and not meant to be limiting, the control algorithm maytake the form:Torque Command=K×(C+O)

-   -   where        -   K=gain,        -   C=a vector defining the loaded support platform's center of            gravity with respect to a fiducial point on the transporter,            and        -   O=offset.

The loaded support platform's position of center of gravity, C, may bein the form of an error term defined as the loaded platform's desiredposition of center of gravity minus the loaded platform's sensedposition of center of gravity. The loaded platform's desired position ofcenter of gravity may be a predetermined constant in the controlalgorithm. Alternatively, a subject on the transporter may control thesetting of the platform's desired position of center of gravity via userinterface 41. For example, upon stepping onto the platform and prior toallowing movement of the transporter, a subject may activate a switch onthe transporter's handlebar that triggers determination of the desiredposition of center of gravity based on inputs received from the sensormodule 44. This allows the subject to acquire a known initial position,from which the subject can then deviate so as to cause a change in theloaded platform's position of center of gravity.

The gain, K, may be a predetermined constant, or may be entered/adjustedby the operator through user interface 41. Gain K is, most generally, avector, with the torque determined as a scalar product of the gain andthe center-of-gravity displacement vector. Responsiveness of thetransporter to changes in the loaded support platform's center ofgravity can be governed by K. For example, if the magnitude of at leastone element of vector K is increased, a rider will perceive a stifferresponse in that a small change in the loaded platform's position ofcenter of gravity will result in a large torque command.

Offset, O, may be incorporated into the control algorithm to govern thetorque applied to the motorized drive, either in addition to, orseparate from, the direct effect of C. Thus, for example, the user mayprovide an input by means of a user interface 41 of any sort, the inputbeing treated by the control system equivalently to a change, forexample, in the loaded platform's position of center of gravity.

Thus, in the above-described embodiments of the invention, motion of thetransporter may be controlled by changing the loaded platform's centerof gravity, such as by the operator leaning or alternatively, changinghis position on the platform. Depending on the control algorithm, aninitial change in the center of gravity in the fore direction may resultin positive torque being applied to at least one of the wheels, causingthe wheels to move forwards. Likewise, an initial change in the centerof gravity in the aft direction may result in a negative torque appliedto at least one of the wheels, causing the wheels to move in the aftdirection. If the subject then continues to lean (or remains in hischanged position on the platform) such that the center of gravity of theloaded platform remains the same, the motor will continue to torque atapproximately the same rate.

As described above, in addition to being statically stable in thefore-aft plane, the transporter may also be statically stable withrespect to tipping in the lateral plane, with a signal representative ofthe position of the center of gravity being determined in either or bothfore-aft and lateral directions. In such embodiments, lateral shifts inthe center of gravity of the loaded platform can be used eitherseparately or in combination with shifts in the center of gravity in thefore-aft plane to control motion of the transporter. For example, andnot meant to be limiting, fore-aft shifts in the center of gravity ofthe loaded support platform can control fore-aft motion, while lateralshifts in the center of gravity control steering of the transporter.

Steering may be accomplished in an embodiment having at least twolaterally disposed wheels (i.e., a left and right wheel), by providing,for example, separate motors for left and right wheels. Torque desiredfor the left motor and the torque desired from the right motor can becalculated separately. Additionally, tracking both the left wheel motionand the right wheel motion permits adjustments to be made, as known topersons of ordinary skill in the control arts, to prevent unwantedturning of the vehicle and to account for performance variations betweenthe two motors.

In accordance with another embodiment of the invention, FIG. 5 shows atransporter 501 that includes a support platform 502 capable ofsupporting a load. The support platform 501 is coupled to a plurality ofwheels 503 and 504 and is statically stable with respect to tipping inboth the fore-aft and lateral planes. A pivot element 507 is pivotallycoupled to at least one of the wheels 503 and 504, such that the pivotelement 507 is capable of tilting. For example, the plurality of groundcontacting elements may include two laterally disposed wheels, rightwheel 504 and left wheel (not shown), rotatable around an axis 545,wherein the pivot element 507 is pivotally coupled to the axis 545 suchthat pivot element 507 can tilt in the fore-aft plane.

Tilting of the pivot element 507 is accomplished via an operatorinterface, which may be, without limitation, a handlebar 512. Handlebar512 is coupled to the pivot element 507 such that, for example, a tiltof the handlebar 512 in the fore-aft direction results in acorresponding tilt of pivot element 507.

At least one sensor 555 generates a signal indicative of the tilt of thepivot element 507. Sensor 555 may be, without limitation: a spring andassociated sensor (such as a distance sensor); a load sensor; a tiltsensor such as an inclinometer or a gyroscope which provides aninclination of the support platform 507; whiskers; an angular ratesensor; and/or non-contact sensors, such as ultra-sonic or optical. Thetilt may be measured, without limitation, relative to gravity, theground, and/or a reference on the transporter, such as a positionproximate the axis of rotation. A controller controls a motorized drivearrangement drives at least one wheel 504 based at least on the tilt.

In various embodiments, the pivot element 507 is flexibly coupled tosupport platform 502, for example, by a plurality of springs 508-509.This allows the pivot element platform 507 to maintain a predeterminedtilt when the handlebar 512 is not manipulated. In various embodiments,the controller may be preset so as to command a specified motion basedon the predetermined tilt. For example, when the predetermined tilt issensed, controller may command no motion to the motorized drivearrangement. Responsiveness of the transporter can also be controlledvia springs 508-509.

As in above-described embodiments, steering of the transporter 501 maybe controlled by any number of user interfaces known in the art, suchas, without limitation, a joystick or thumbwheel positioned on or inclose proximity to the handlebar. Motorized drive arrangement may haveseparate motors, as described above, for separately driving laterallydisposed left (not shown) and right wheels 504 based on signals receivedfrom the user interface. Laterally disposed left wheel (not shown) andright wheel 503 may be, for example, caster wheels that are capable ofturning around a vertical axis to support turning of transporter 501.

In above-described embodiments of the invention, the transporter mayinclude an indicator, referred to as reference number 540 in FIG. 5.Indicator 540 is apprehensible externally, based on motion commanded viathe motorized drive arrangement. For example, the indicator 540 may bebased on acceleration commanded. The externally apprehensible indication540 may include, without limitation, a light that can be illuminated.

The described embodiments of the invention are intended to be merelyexemplary and numerous variations and modifications will be apparent tothose skilled in the art. All such variations and modifications areintended to be within the scope of the present invention as defined inthe appended claims.

1. A transporter comprising: a support platform for supporting a load,the loaded support platform defining fore-aft and lateral planes andcharacterized by a tilt with respect to the ground and a loaddistribution, the load distribution determining the tilt; a plurality ofground contacting elements coupled to the support platform such that thetransporter is statically stable with respect to tipping in the fore-aftplace; a motorized drive arrangement for driving at least one of theplurality of ground contacting elements; a sensor module for generatinga signal indicative of the load distribution of the loaded supportplatform based upon the tilt of the platform; and a controller forcommanding the motorized drive arrangement based on the loaddistribution.
 2. The transporter according to claim 1, wherein theplurality of ground contacting elements include at least two wheels. 3.The transporter according to claim 2, wherein the at least two wheelsinclude: a first wheel rotatable about a first axis; and a second wheelrotatable about a second axis, the second axis disposed aft of the firstaxis.
 4. The transporter according to claim 1, wherein the controller isconfigured so that fore and aft motion of the transporter is controlledby shifting the load distribution of the loaded support platform foreand aft.
 5. The transporter according to claim 1, wherein the loadedsupport platform is characterized by a center of gravity having aposition, and wherein the controller is configured so that fore and aftmotion of the transporter is controlled by shifting the position of thecenter of gravity of the loaded support platform fore and aft.
 6. Thetransporter according to claim 1, wherein the controller is configuredso that turning of the transporter is controlled by laterally shiftingthe load distribution of the loaded support platform.
 7. The transporteraccording to claim 1, wherein the loaded support platform ischaracterized by a center of gravity having a position, wherein thecontroller is configured so that turning of the transporter iscontrolled by laterally shifting the position of the center of gravityof the loaded support platform.
 8. The transporter according to claim 1,wherein the plurality of ground connecting elements are coupled to thesupport platform such that the transporter is statically stable withrespect to tipping in both the fore-aft and lateral planes.
 9. Thetransporter according to claim 1, wherein the sensor module includes atilt sensor.
 10. The transporter according to claim 1, wherein thesensor module adds an offset in generating the signal.
 11. Thetransporter according to claim 10, wherein the offset is adjustable viaa user interface.
 12. The transporter according to claim 1, wherein thecontroller commands the motorized drive arrangement so as to cause anacceleration of the transporter, the transporter further including anindicator for providing an indication based on the acceleration, theindication apprehensible externally.
 13. The transporter according toclaim 1, wherein the indicator is viewable from behind the transporter.14. The transporter according to claim 1, wherein the transporterfurther includes a user interface, wherein the controller commands themotorized drive arrangement based at least on a signal provided by theuser interface.
 15. A transporter according to claim 14, wherein theuser interface is selected from the group of user interfaces consistingof a joystick and a dial.
 16. A method for controlling a transporterhaving a support platform for supporting a load, the loaded supportplatform defining fore-aft and lateral planes and characterized by aload distribution, the transporter further including a plurality ofground-contacting elements such that the transporter is staticallystable with respect to tipping in the fore-aft plane, the transporterfurther including a motorized drive arrangement for driving at least oneof the plurality of ground-contacting elements, the method comprising:determining a tilt with respect to the ground of the loaded support, theload distribution determining the tilt; and commanding the motorizeddrive arrangement based at least on the tilt indicative of the loaddistribution.
 17. The method according to claim 16, wherein determiningthe load distribution of the loaded platform includes sensing a loadabove at least one ground-contacting element.
 18. The method accordingto claim 16, wherein determining the load distribution of gravity of theloaded platform includes sensing a tilt of the loaded support platform.19. The method according to claim 16, wherein determining the loaddistribution of the loaded platform includes sensing a roll angle of theloaded support platform.
 20. The method according to claim 16, whereincommanding the motorized drive is further based on a control signal froma transporter user interface.
 21. The method according to claim 16,further comprising providing an externally apprehensible indicationbased on motion commanded.
 22. The method according to claim 21, whereinproviding the externally apprehensible indication is based onacceleration commanded.
 23. A vehicle comprising: a first platform; aplurality of ground contacting elements coupled to the first platform; asecond platform for supporting a rider, the second platform locatedabove the first platform; a sensor module interposed between the firstplatform and the second platform, the sensor module generating a weightshift signal indicative of weight shifting by the rider on the secondplatform; and a motorized drive arrangement for driving at least one ofthe plurality of ground contacting elements; a controller for commandingthe motorized drive arrangement based on the signal generated by thesensor indicative of the weight shift.
 24. A vehicle according to claim23, wherein the motorized drive arrangement is configured to control atleast one of steering motion and straight motion.
 25. A vehicleaccording to claim 23, wherein the sensor module includes a load sensor.